The present invention relates to polymer nanoparticles and methods for their preparation. The invention advantageously provides mechanisms for surface modifications, functionalization, and general characteristic tailoring to improve performance in various host compositions.
Polymer nanoparticles have attracted increased attention over the past several years in a variety of fields including catalysis, combinatorial chemistry, protein supports, magnets, and photonic crystals. Similarly, vinyl aromatic (e.g. polystyrene) microparticles have been prepared for uses as a reference standard in the calibration of various instruments, in medical research and in medical diagnostic tests. Such polystyrene microparticles have been prepared by anionic dispersion polymerization and emulsion polymerization.
Nanoparticles can be discrete particles uniformly dispersed throughout a host composition. Nanoparticles preferably are monodisperse in size and uniform in shape. However, controlling the size of nanoparticles during polymerization and/or the surface characteristics of such nanoparticles can be difficult. Accordingly, achieving better control over the surface composition of such polymer nanoparticles also is desirable.
Rubbers may be advantageously modified by the addition of various polymer compositions. The physical properties of rubber moldability and tenacity are often improved through such modifications. Of course, however, the simple indiscriminate addition of nanoparticles to rubber is likely to cause degradation of the matrix material, i.e., the rubber, characteristics. Moreover, it is expected that primarily the selection of nanoparticles having suitable size, material composition, and surface chemistry, etc., will improve the matrix characteristics.
In this regard, development of nanoparticles having a outer layer which would be compatible with a wide variety of matrix materials is desirable because discrete particles could likely disperse evenly throughout the host to provide a uniform matrix composition. However, the development of a process capable of reliably producing acceptable nanoparticles has been a challenging endeavor. For example, the solubility of various monomers in traditional alkane solvents has made solution polymerization a difficult process by which to achieve nanoparticles having a variety of outer layers. Moreover, the development of a solution polymerization process producing reliable nanoparticles, particularly nanoparticles advantageously employed in rubber compositions, has been elusive.
Commonly owned U.S. Pat. No. 6,437,050 is directed to polymer nanoparticles and a method of forming nanoparticles with desired surface characteristics and size. Commonly owned U.S. patent application Ser. No. 10/223,393 (filed Aug. 19, 2002) includes a method of controlling the surface characteristics of polymer nanoparticles via surface functionalization. In this application the functional groups remain inside the nanoparticle in the form of an organic reaction residue.
Nano-scale metal composites have also been used advantageously in a variety of fields including, but not limited to, information technology, medicine and health, material and manufacturing, aeronautics and space exploration, environmental, and energy fields. Formation of nano-scale metal composites has often proven difficult due to the expense and difficulty of creating known templates, as well as the often difficult step of separating the composites from the template.
Accordingly, it would be desirable to develop polymer nanoparticles with desirable surface characteristics and size. It would also be desirable to develop a process for using these nanoparticles as templates to produce nano-scale metal composites.